One of the main applications of the invention is treating plates essentially for cleaning purposes, which plates are in the form of flat disks of the semiconductor type as used for making integrated circuits. However, other applications are possible, e.g. for treating flat glass screens such as those for monitors or television sets, or optical disks, or hard disks as used in computing, or any other thin-film part providing it can be defined as being a flat part of regular shape.
The material from which the plates are made may be a ceramic, silicon, or some other material; they are slices cut very finely and then coated, etched, and/or cleaned.
These various operations must be performed with the best possible efficiency in as short a time as possible, firstly to improve the reliability of the resulting plates and secondly to reduce manufacturing costs.
In the description below, methods and devices relating to cleaning semiconductor plates are described essentially with reference to the prior art, however it is clear that, as specified by the claims, the present invention is applicable to any other regularly-shaped circular flat part such as flat screens, solar filters, optical disks, etc. and also to other chemical treatments of such parts, and not only to cleaning.
Various methods and devices are known for cleaning plates in which the plates are handled and transferred from one workstation to another in support-baskets from which they are extracted singularly or in groups for treatment in each workstation.
Cleaning operations are very difficult to perform since the particles to be removed are very small, arising (even when there is no external pollution) e.g. from an etching operation, which particles must not be left in the grooves created in this way in the plates, which grooves are themselves very fine, since a single such particle can give rise to an interfering electrical contact that prevents a portion of the plate concerned being usable and thus requires the plate to be rejected.
Cleaning is essential for this purpose, is critical, and is performed in a sealed clean room using three different types of method:
the plate-by-plate method which consists in treating the plates one-by-one in succession in cleaning chambers placed side-by-side, thereby constituting an operation that is lengthy, that requires a large amount of space, and many handling operations; PA1 the tank-by-tank method which consists in performing the same operations as above, but displacing the plates while they are grouped together in baskets, thereby enabling the operations to be performed more quickly than in the preceding method, but still needing a large amount of space for the various cleaning tanks; and PA1 the method using a central reactor, as in the present invention, which method is currently the preferred method since it takes up less space in a clean room where space is at a premium and it enables the drying operation to be accelerated: instead of moving baskets of plates as in the preceding method through a plurality of successive cleaning tanks, possibly including different cleaning substances and taking up a great deal of space, each basket is enclosed in succession in a chamber or vat within which cleaning fluids are sprayed onto the plates or which is filled with cleaning fluid until the baskets are immersed; once the various treatment operations have been performed and the cleaning substances removed from the inside volume of the chamber, the plates are dried by centrifuging the basket. PA1 said flat parts stored in a transport basket are brought beneath said chamber which is opened by moving the shell constituting the chamber away from its closure means; PA1 said parts are transferred by any suitable means from the basket into the open volume of said chamber; PA1 said parts are grasped by tilting two lateral combs that were previously moved apart, and which engage beneath said parts so as to constitute support means for them, and said transfer means is withdrawn; PA1 said chamber is closed by moving said shell over said parts and their supporting combs until contact is made against the closure means, and the assembly is sealed; and PA1 treatment is performed by injecting fluids into the chamber using said means for injecting treatment fluids, then at the end of treatment after the fluids have been discharged by said discharge means and after the chamber has been reopened, said parts are transferred back down into their transport basket.
Various types of apparatus using the above method are described in European patent application EP 0 047 308 filed under U.S. priority of Feb. 27, 1981, and EP 0 292 090 filed under U.S. priority of Feb. 29, 1988, by a company named Semitool.
In such "washing machine" type devices, as in others using the same principle of drying by centrifuging, the plates are initially transferred from their transport baskets into another basket specific to the device and serving not only to hold the plates in place during centrifuging, but also to transmit rotary motion to them.
That method therefore requires two handling operations for transferring plates from one basket to another since the basket for transporting plates from one workstation to another is also specific to that purpose, the mechanics are therefore complex to implement and there are problems of equilibrium and of inertia. In addition, because of their volume and size, the mechanical parts mask the plates to be cleaned to some extent, thereby making it impossible to guarantee that cleaning is uniform or that the quality of the operation is repeatable.
The problem to be solved is thus that of being capable of performing operations of treating and/or cleaning any regularly-shaped flat parts in a chamber of a "central reactor" device, while making use of as few intermediate mechanical parts as possible, while performing as few handling operations as possible on said flat parts to be treated and/or cleaned, and while obtaining optimum quality with respect to repeatability and uniformity in the treatment and/or cleaning.